American Board of Internal Medicine (ABIM) Certification Practice Exam

Which method is considered the gold standard for diagnosing gout?

1. Joint X-ray

2. Synovial fluid analysis

3. Serum uric acid level

4. Clinical symptoms evaluation

The correct answer is: Synovial fluid analysis

The gold standard for diagnosing gout is synovial fluid analysis. This method involves the aspiration of fluid from an inflamed joint, typically using a needle, followed by examination under polarized light microscopy. This analysis allows for the direct identification of monosodium urate crystals, which are indicative of gout. The presence of these crystals in the synovial fluid confirms the diagnosis and distinguishes gout from other types of inflammatory arthritis. While other methods like serum uric acid level measurement can support the diagnosis, especially in indicating hyperuricemia, they are not definitive on their own because not all individuals with elevated uric acid levels develop gout. Similarly, the evaluation of clinical symptoms can suggest gout but is not sufficiently specific, as many other conditions can produce similar symptoms of joint inflammation. Joint X-rays might reveal damage or changes consistent with chronic gout but do not confirm the presence of urate crystals. The importance of synovial fluid analysis lies in its ability to provide definitive evidence of the crystalline nature of the precipitating factors in gout, making it the most reliable diagnostic method available.